From 1942 onwards German air space was an unlimited target area for the Allied bombing units. In 1943 the design department of the Messerschmitt aircraft factory was working on a further development of the Me 262 and the project was designated the Me P.1099, a two seat, all-weather fighter which was to operate against the Allied bombers. In 1944 a concept was produced for a heavy fighter with rear firing attack weapons. The armament consisted of 2 rear firing MG FPL 151s, one forward firing MG FHL 151 and two MK 103 Zs also rear firing. The power plant, as a transitional solution for the unsuccessful Heinkel Hirth type HeSO11 engines, was to be twin Junkers Jumo 004 C jet engines. The speed was to be between 870 and 930 km/h at an altitude of 6,500 m.